The present invention relates to adaptive video delivery, and in particular to an apparatus, system and method for supplying video images to multiple users across a network.
The satisfactory delivery of video to multiple users across a network which has no guaranteed level of service has historically been difficult to achieve. Broadcasting the video across the network is typically unsatisfactory since not all recipients will necessarily be able to handle the data at the same bit rates. Even where they could theoretically do so, different levels of congestion at different points across the network may mean that in practice the bit rate that can actually be delivered varies between recipients. Furthermore, the actual bit rate available to each recipient will normally vary with time, as the level of congestion across the network varies. The result is that users see unacceptable “gaps” or “jumps” in the video transmission.
Conventional attempts to address this problem (as used for example in the transmission of web-cam video across the internet) rely on the individual transmission to each user of a sequence of still images at a rate the user can accept. When the recipient has received the first image, a message is sent back across the internet to the web-cam server, requesting the next, and so on.
Such a method is inefficient in its use of network band width, and is incapable of making use of time-dependent video compression techniques such as are used for example in motion-compensated video compression.